1. Field of the Invention
The present invention relates to a mail feeding device for feeding a plurality of accumulated mail items one by one.
2. Description of the Related Art
A mail feeding device is known in which a belt with holes is run along mail items to hold them one by one, using a suction nozzle provided at the reverse side of the belt, thereby sequentially picking up them (see, for example, U.S. Pat. No. 5,391,051). In this device, a solenoid valve for executing on/off control of negative pressure is provided between a vacuum tank and the suction nozzle.
In this structure, to pick up each mail item, the belt is run, the solenoid valve is opened, and the suction nozzle is operated to hold each mail item on the belt using a suction force. Further, to continuously feed mail items, the solenoid valve is closed regularly in accordance with the feeding timing of each mail item, thereby providing gaps between subsequently fed mail items.
However, in the above structure, even if the solenoid valve is closed to stop suction by the suction nozzle, negative pressure applied to a mail item cannot quickly be eliminated where the mail item is held by the belt by a suction force. Accordingly, even if the on/off cycle of the solenoid valve is shortened to feed mail items at high speed, high-speed feeding of mail items cannot be realized since negative pressure applied to the mail items cannot quickly be eliminated.